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The Internet-of-Things (IoT) applications require orientation-insensitive wireless devices to maintain stable and reliable communication. For those reasons, antennas providing a wide quasi-isotropic and circular polarization (CP) coverage are very attractive. However, achieving wide quasi-isotropic and CP coverage simultaneously is challenging. In this work, we show that properly designed sloped dipoles on a 3-D structure can maximize the CP coverage (theoretically up to 100%) even with equal-phased feed to the dipole elements. We derive the conditions and present the design graphs for the optimum slope angle for the dipole elements on a 3-D hexagonal-shaped package to achieve a wide quasi-isotropic and CP coverage simultaneously. Based on the proposed theory, a practical antenna has been designed and fabricated using additive manufacturing. The measured results demonstrate a 7 dB isotropy of 92% and a CP coverage of 85%, which matches well with the predicted results from the theoretical analysis and full-wave simulations. [ABSTRACT FROM AUTHOR]

In this letter, a high-aperture-efficiency (ηAP), right-hand circularly polarized (RHCP), sequentially rotated hexagonal microstrip antenna array, working at GPS L1 band, is proposed. The proposed antenna design is placed on the hexagonal top of a floating sensor node for ocean and marine monitoring applications. To use the hexagonal area effectively and maximize the ηAP, CP microstrip antenna elements have been distributed centrosymmetric about the origin on the hexagonal substrate. Typically, the ηAP is enhanced by using thicker substrates, particularly with air gaps. Here, we show a high ηAP on a very low-profile substrate (0.011 λ for the lowest operating frequency) by properly choosing the distance of the antenna elements from the center of the array. The proposed design, based on H-shaped aperture-coupled circular patches, demonstrates a measured gain of 12.4 dBi and an ηAP of 101%, which is one of the highest reported ηAP for one of the lowest profile sequentially rotational array. [ABSTRACT FROM AUTHOR]

A low-cost and additively manufactured three-dimensional (3-D) antenna-in-package with quasi-isotropic radiation is proposed for a marine animals monitoring system. The antenna is based on a meandered dipole folded as a split-ring resonator structure, which can generate simultaneously a pair of orthogonal electric and magnetic dipoles, thus providing a quasi-isotropic radiation pattern. The antenna (integrated with a balun) has been inkjet-printed on a 3-D-printed buoyant cone structure, which acts also as the system package to house the electronics and the battery. The antenna designed at 2.4 GHz is electrically small, with a $ka\; = 0.49$ , and has a bandwidth of 70 MHz (2.9%). The measured gain deviation of the antenna (maximum to minimum) is near 3 dB in bandwidth, thus qualifying it as a quasi-isotropic antenna. Field tests of the antenna in the active state (integrated with the electronics) confirm a reliable communication range of 240 m in any direction in the azimuthal plane. [ABSTRACT FROM AUTHOR]